1. Technical Field
The present invention relates to electro-optical devices and electronic apparatuses.
2. Related Art
Electro-optical devices for liquid crystal display apparatuses have been known. The electro-optical devices include, for example, a liquid crystal panel, and a backlight for supplying light to the liquid crystal panel.
The liquid crystal panel includes an element substrate having thin film transistors (TFTs) serving as switching elements, described below, arranged in a matrix, a counter substrate facing the element substrate, and a liquid crystal as an electro-optical material disposed between the element substrate and the counter substrate.
The element substrate includes a plurality of scanning lines disposed at predetermined intervals, and a plurality of data lines crossing those scanning lines and disposed at predetermined intervals.
Pixels are disposed at intersections of the scanning lines and the data lines. Each of the pixels includes the TFT described above, and a pixel electrode. The pixels are arranged in a matrix to form a display area. Gate electrodes of the TFTs are connected to the scanning lines, and source electrodes of the TFTs are connected to the data lines. Drain electrodes of the TFTs are connected to the pixel electrodes.
The counter substrate includes a common electrode disposed so as to face the pixel electrodes.
The electro-optical devices operate as follows: a selection voltage is supplied to the scanning lines in a line-sequential manner to select all the pixels corresponding to a desired one of the scanning lines. Image signals are supplied to the data lines in synchronization with the selection of the pixels. Thus, the image signals are supplied to all the pixels selected by the selection voltage, thereby writing image data to the pixel electrodes.
When the image data is written to the pixel electrodes, due to the difference in potential between the pixel electrodes and the common electrode, drive voltages are applied to the liquid crystal. This changes the alignment or orientation of the liquid crystal to change the light from the backlight transmitted through the liquid crystal, thus achieving gradation display.
One of those electro-optical devices is a liquid crystal panel having a touch key function (see, for example, JP-A-11-119898).
In a touch panel disclosed in JP-A-11-119898, an area sensor is disposed on the liquid crystal panel. The area sensor includes photoelectric conversion elements disposed at predetermined intervals for converting light into electrical signals.
When an input pen is operated on a display screen of the liquid crystal panel, the light from the backlight is reflected by the tip of the input pen, and the reflected light is converted into an electrical signal by the corresponding photoelectric conversion element. The electrical signal is detected to specify the position of the input pen on the area sensor.
The visibility of the display of electro-optical devices depends on the ambient brightness around the electro-optical devices based on ambient light such as sunlight. That is, as the ambient brightness around the electro-optical devices increases, the contrast between the brightness of the display areas of the electro-optical devices and the ambient brightness around the electro-optical devices is reduced, resulting in low visibility of the display of the electro-optical devices.
One solution to overcome this problem is to measure the ambient light intensity to adjust the contrast between the brightness of the display area and the ambient brightness. However, the electro-optical device disclosed in JP-A-11-119898 is not configured to measure the ambient light intensity and it is therefore difficult to increase the visibility of the display.